Actual source code: ex1.c
1: static char help[] = "An example of hybrid system using TS event.\n";
3: /*
4: The dynamics is described by the ODE
5: u_t = A_i u
7: where A_1 = [ 1 -100
8: 10 1 ],
9: A_2 = [ 1 10
10: -100 1 ].
11: The index i changes from 1 to 2 when u[1]=2.75u[0] and from 2 to 1 when u[1]=0.36u[0].
12: Initially u=[0 1]^T and i=1.
14: Reference:
15: I. A. Hiskens, M.A. Pai, Trajectory Sensitivity Analysis of Hybrid Systems, IEEE Transactions on Circuits and Systems, Vol 47, No 2, February 2000
16: */
18: #include <petscts.h>
20: typedef struct {
21: PetscScalar lambda1;
22: PetscScalar lambda2;
23: PetscInt mode; /* mode flag*/
24: } AppCtx;
26: PetscErrorCode EventFunction(TS ts, PetscReal t, Vec U, PetscReal *fvalue, void *ctx)
27: {
28: AppCtx *actx = (AppCtx *)ctx;
29: const PetscScalar *u;
31: PetscFunctionBegin;
32: PetscCall(VecGetArrayRead(U, &u));
33: if (actx->mode == 1) {
34: fvalue[0] = PetscRealPart(u[1] - actx->lambda1 * u[0]);
35: } else if (actx->mode == 2) {
36: fvalue[0] = PetscRealPart(u[1] - actx->lambda2 * u[0]);
37: }
38: PetscCall(VecRestoreArrayRead(U, &u));
39: PetscFunctionReturn(PETSC_SUCCESS);
40: }
42: PetscErrorCode PostEventFunction(TS ts, PetscInt nevents, PetscInt event_list[], PetscReal t, Vec U, PetscBool forwardsolve, void *ctx)
43: {
44: AppCtx *actx = (AppCtx *)ctx;
46: PetscFunctionBegin;
47: if (actx->mode == 1) {
48: actx->mode = 2;
49: PetscCall(PetscPrintf(PETSC_COMM_SELF, "Change from mode 1 to 2 at t = %f \n", (double)t));
50: } else if (actx->mode == 2) {
51: actx->mode = 1;
52: PetscCall(PetscPrintf(PETSC_COMM_SELF, "Change from mode 2 to 1 at t = %f \n", (double)t));
53: }
54: PetscFunctionReturn(PETSC_SUCCESS);
55: }
57: /*
58: Defines the ODE passed to the ODE solver
59: */
60: static PetscErrorCode IFunction(TS ts, PetscReal t, Vec U, Vec Udot, Vec F, void *ctx)
61: {
62: AppCtx *actx = (AppCtx *)ctx;
63: PetscScalar *f;
64: const PetscScalar *u, *udot;
66: PetscFunctionBegin;
67: /* The next three lines allow us to access the entries of the vectors directly */
68: PetscCall(VecGetArrayRead(U, &u));
69: PetscCall(VecGetArrayRead(Udot, &udot));
70: PetscCall(VecGetArray(F, &f));
72: if (actx->mode == 1) {
73: f[0] = udot[0] - u[0] + 100 * u[1];
74: f[1] = udot[1] - 10 * u[0] - u[1];
75: } else if (actx->mode == 2) {
76: f[0] = udot[0] - u[0] - 10 * u[1];
77: f[1] = udot[1] + 100 * u[0] - u[1];
78: }
80: PetscCall(VecRestoreArrayRead(U, &u));
81: PetscCall(VecRestoreArrayRead(Udot, &udot));
82: PetscCall(VecRestoreArray(F, &f));
83: PetscFunctionReturn(PETSC_SUCCESS);
84: }
86: /*
87: Defines the Jacobian of the ODE passed to the ODE solver. See TSSetIJacobian() for the meaning of a and the Jacobian.
88: */
89: static PetscErrorCode IJacobian(TS ts, PetscReal t, Vec U, Vec Udot, PetscReal a, Mat A, Mat B, void *ctx)
90: {
91: AppCtx *actx = (AppCtx *)ctx;
92: PetscInt rowcol[] = {0, 1};
93: PetscScalar J[2][2];
94: const PetscScalar *u, *udot;
96: PetscFunctionBegin;
97: PetscCall(VecGetArrayRead(U, &u));
98: PetscCall(VecGetArrayRead(Udot, &udot));
100: if (actx->mode == 1) {
101: J[0][0] = a - 1;
102: J[0][1] = 100;
103: J[1][0] = -10;
104: J[1][1] = a - 1;
105: } else if (actx->mode == 2) {
106: J[0][0] = a - 1;
107: J[0][1] = -10;
108: J[1][0] = 100;
109: J[1][1] = a - 1;
110: }
111: PetscCall(MatSetValues(B, 2, rowcol, 2, rowcol, &J[0][0], INSERT_VALUES));
113: PetscCall(VecRestoreArrayRead(U, &u));
114: PetscCall(VecRestoreArrayRead(Udot, &udot));
116: PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
117: PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
118: if (A != B) {
119: PetscCall(MatAssemblyBegin(B, MAT_FINAL_ASSEMBLY));
120: PetscCall(MatAssemblyEnd(B, MAT_FINAL_ASSEMBLY));
121: }
122: PetscFunctionReturn(PETSC_SUCCESS);
123: }
125: int main(int argc, char **argv)
126: {
127: TS ts; /* ODE integrator */
128: Vec U; /* solution will be stored here */
129: Mat A; /* Jacobian matrix */
130: PetscMPIInt size;
131: PetscInt n = 2;
132: PetscScalar *u;
133: AppCtx app;
134: PetscInt direction[1];
135: PetscBool terminate[1];
137: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
138: Initialize program
139: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
140: PetscFunctionBeginUser;
141: PetscCall(PetscInitialize(&argc, &argv, (char *)0, help));
142: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
143: PetscCheck(size == 1, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "Only for sequential runs");
144: app.mode = 1;
145: app.lambda1 = 2.75;
146: app.lambda2 = 0.36;
147: PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "ex1 options", "");
148: {
149: PetscCall(PetscOptionsReal("-lambda1", "", "", app.lambda1, &app.lambda1, NULL));
150: PetscCall(PetscOptionsReal("-lambda2", "", "", app.lambda2, &app.lambda2, NULL));
151: }
152: PetscOptionsEnd();
154: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
155: Create necessary matrix and vectors
156: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
157: PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
158: PetscCall(MatSetSizes(A, n, n, PETSC_DETERMINE, PETSC_DETERMINE));
159: PetscCall(MatSetType(A, MATDENSE));
160: PetscCall(MatSetFromOptions(A));
161: PetscCall(MatSetUp(A));
163: PetscCall(MatCreateVecs(A, &U, NULL));
165: PetscCall(VecGetArray(U, &u));
166: u[0] = 0;
167: u[1] = 1;
168: PetscCall(VecRestoreArray(U, &u));
169: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
170: Create timestepping solver context
171: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
172: PetscCall(TSCreate(PETSC_COMM_WORLD, &ts));
173: PetscCall(TSSetProblemType(ts, TS_NONLINEAR));
174: PetscCall(TSSetType(ts, TSCN));
175: PetscCall(TSSetIFunction(ts, NULL, (TSIFunctionFn *)IFunction, &app));
176: PetscCall(TSSetIJacobian(ts, A, A, (TSIJacobianFn *)IJacobian, &app));
178: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
179: Set initial conditions
180: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
181: PetscCall(TSSetSolution(ts, U));
183: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
184: Set solver options
185: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
186: PetscCall(TSSetMaxTime(ts, 0.125));
187: PetscCall(TSSetExactFinalTime(ts, TS_EXACTFINALTIME_MATCHSTEP));
188: PetscCall(TSSetTimeStep(ts, 1. / 256.));
189: PetscCall(TSSetFromOptions(ts));
191: /* Set directions and terminate flags for the two events */
192: direction[0] = 0;
193: terminate[0] = PETSC_FALSE;
194: PetscCall(TSSetEventHandler(ts, 1, direction, terminate, EventFunction, PostEventFunction, (void *)&app));
196: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
197: Run timestepping solver
198: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
199: PetscCall(TSSolve(ts, U));
201: /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
202: Free work space. All PETSc objects should be destroyed when they are no longer needed.
203: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
204: PetscCall(MatDestroy(&A));
205: PetscCall(VecDestroy(&U));
206: PetscCall(TSDestroy(&ts));
208: PetscCall(PetscFinalize());
209: return 0;
210: }
212: /*TEST
214: build:
215: requires: !complex
216: test:
217: args: -ts_monitor
219: test:
220: suffix: 2
221: args: -ts_monitor_lg_solution -1
222: requires: x
224: TEST*/